Of the three CBs I've owned or had the chance to ride over a period of time... they all had some amount of front end shake when letting hands off on deceleration. I told a competent Honda tech about it once and he said 'well, don't take your hands off.' Fair enough.
That said, there are a lot of good suggestions here on how to attempt to remedy and it sounds like you've done some (swing arm rebuild, front bearings). When you change tires I would change out rear bearings if needed. There's always the head bearings, as mentioned, and a fork brace for other reasons. If you do all of those at once - tires, rear bearings and head bearings - you may never know what the cause was. And there's always the chance it may still be present. There's so many potential things. Rims and spokes, wheel truing and balancing might need to be on the list as well. I don't think it's a lost cause though. If it's a scary/significant shake I'm sure you'll get it resolved. If it's mild, maybe not. It's subjective as to how bad it is.
On my 750 I had the normal (what I call normal) front end shake on deceleration with hands off handlebar. I had my rims rebuilt with new spokes and trued along with new All Balls bearings front and rear - shake went away and bike just instantly 'felt better'. Did not change head bearings or swing arm bushings.
Check out Metzeler for tires. Many here, myself included, use the Lasertec. They come in standard stock size. Tread pattern is not too modern and they offer good performance. They also have a classic line that is available in some places. I haven't heard bad things about the K70s, but it is more designed for gravel road use vs. regular street. However, a friend of mine uses them and prefers them to the Metzeler Lasertec.
[And to clarify: 'Hands off handlebar' just means slightly off, still touching grips; not throwing hands in the air on decel.]
